Carrier billing lets you buy apps, games, or digital content by charging the...

https://camilassmartthoughtss.opalvector.com/posts/why-does-my-checkout-ask-me-to-confirm-by-text-message

Carrier billing lets you buy apps, games, or digital content by charging the cost directly to your phone bill. If you have a monthly plan, the purchase appears on your next bill. For pay-as-you-go users, the amount is deducted from your available credit